draft-ietf-roll-aodv-rpl-10.txt   draft-ietf-roll-aodv-rpl-11.txt 
ROLL S. Anamalamudi ROLL S. Anamalamudi
Internet-Draft SRM University-AP Internet-Draft SRM University-AP
Intended status: Standards Track M. Zhang Intended status: Standards Track C. Perkins
Expires: October 6, 2021 Huawei Technologies Expires: March 20, 2022 Lupin Lodge
C. Perkins
Lupin Lodge
S.V.R.Anand S.V.R.Anand
Indian Institute of Science Indian Institute of Science
B. Liu B. Liu
Huawei Technologies Huawei Technologies
April 4, 2021 September 16, 2021
Supporting Asymmetric Links in Low Power Networks: AODV-RPL Supporting Asymmetric Links in Low Power Networks: AODV-RPL
draft-ietf-roll-aodv-rpl-10 draft-ietf-roll-aodv-rpl-11
Abstract Abstract
Route discovery for symmetric and asymmetric Point-to-Point (P2P) Route discovery for symmetric and asymmetric Peer-to-Peer (P2P)
traffic flows is a desirable feature in Low power and Lossy Networks traffic flows is a desirable feature in Low power and Lossy Networks
(LLNs). For that purpose, this document specifies a reactive P2P (LLNs). For that purpose, this document specifies a reactive P2P
route discovery mechanism for both hop-by-hop routing and source route discovery mechanism for both hop-by-hop routing and source
routing: Ad Hoc On-demand Distance Vector Routing (AODV) based RPL routing: Ad Hoc On-demand Distance Vector Routing (AODV) based RPL
protocol (AODV-RPL). Paired Instances are used to construct protocol (AODV-RPL). Paired Instances are used to construct
directional paths, in case some of the links between source and directional paths, for cases where there are asymmetric links between
target node are asymmetric. source and target nodes.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 6, 2021. This Internet-Draft will expire on March 20, 2022.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 34 skipping to change at page 2, line 29
3. Overview of AODV-RPL . . . . . . . . . . . . . . . . . . . . 6 3. Overview of AODV-RPL . . . . . . . . . . . . . . . . . . . . 6
4. AODV-RPL DIO Options . . . . . . . . . . . . . . . . . . . . 6 4. AODV-RPL DIO Options . . . . . . . . . . . . . . . . . . . . 6
4.1. AODV-RPL RREQ Option . . . . . . . . . . . . . . . . . . 6 4.1. AODV-RPL RREQ Option . . . . . . . . . . . . . . . . . . 6
4.2. AODV-RPL RREP Option . . . . . . . . . . . . . . . . . . 8 4.2. AODV-RPL RREP Option . . . . . . . . . . . . . . . . . . 8
4.3. AODV-RPL Target Option . . . . . . . . . . . . . . . . . 10 4.3. AODV-RPL Target Option . . . . . . . . . . . . . . . . . 10
5. Symmetric and Asymmetric Routes . . . . . . . . . . . . . . . 11 5. Symmetric and Asymmetric Routes . . . . . . . . . . . . . . . 11
6. AODV-RPL Operation . . . . . . . . . . . . . . . . . . . . . 13 6. AODV-RPL Operation . . . . . . . . . . . . . . . . . . . . . 13
6.1. Route Request Generation . . . . . . . . . . . . . . . . 13 6.1. Route Request Generation . . . . . . . . . . . . . . . . 13
6.2. Receiving and Forwarding RREQ messages . . . . . . . . . 14 6.2. Receiving and Forwarding RREQ messages . . . . . . . . . 14
6.2.1. General Processing . . . . . . . . . . . . . . . . . 14 6.2.1. General Processing . . . . . . . . . . . . . . . . . 14
6.2.2. Additional Processing for Multiple Targets . . . . . 15 6.2.2. Additional Processing for Multiple Targets . . . . . 16
6.3. Generating Route Reply (RREP) at TargNode . . . . . . . . 16 6.3. Generating Route Reply (RREP) at TargNode . . . . . . . . 16
6.3.1. RREP-DIO for Symmetric route . . . . . . . . . . . . 16 6.3.1. RREP-DIO for Symmetric route . . . . . . . . . . . . 16
6.3.2. RREP-DIO for Asymmetric Route . . . . . . . . . . . . 16 6.3.2. RREP-DIO for Asymmetric Route . . . . . . . . . . . . 17
6.3.3. RPLInstanceID Pairing . . . . . . . . . . . . . . . . 17 6.3.3. RPLInstanceID Pairing . . . . . . . . . . . . . . . . 17
6.4. Receiving and Forwarding Route Reply . . . . . . . . . . 17 6.4. Receiving and Forwarding Route Reply . . . . . . . . . . 18
7. Gratuitous RREP . . . . . . . . . . . . . . . . . . . . . . . 19 7. Gratuitous RREP . . . . . . . . . . . . . . . . . . . . . . . 19
8. Operation of Trickle Timer . . . . . . . . . . . . . . . . . 19 8. Operation of Trickle Timer . . . . . . . . . . . . . . . . . 20
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
9.1. New Mode of Operation: AODV-RPL . . . . . . . . . . . . . 20 9.1. New Mode of Operation: AODV-RPL . . . . . . . . . . . . . 20
9.2. AODV-RPL Options: RREQ, RREP, and Target . . . . . . . . 20 9.2. AODV-RPL Options: RREQ, RREP, and Target . . . . . . . . 21
10. Security Considerations . . . . . . . . . . . . . . . . . . . 20 10. Security Considerations . . . . . . . . . . . . . . . . . . . 21
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22
11.1. Normative References . . . . . . . . . . . . . . . . . . 21 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
11.2. Informative References . . . . . . . . . . . . . . . . . 22 12.1. Normative References . . . . . . . . . . . . . . . . . . 22
12.2. Informative References . . . . . . . . . . . . . . . . . 23
Appendix A. Example: Using ETX/RSSI Values to determine value of Appendix A. Example: Using ETX/RSSI Values to determine value of
S bit . . . . . . . . . . . . . . . . . . . . . . . 23 S bit . . . . . . . . . . . . . . . . . . . . . . . 24
Appendix B. Changelog . . . . . . . . . . . . . . . . . . . . . 24 Appendix B. Changelog . . . . . . . . . . . . . . . . . . . . . 26
B.1. Changes from version 09 to version 10 . . . . . . . . . . 24 B.1. Changes from version 10 to version 11 . . . . . . . . . . 26
B.2. Changes from version 08 to version 09 . . . . . . . . . . 25 B.2. Changes from version 09 to version 10 . . . . . . . . . . 27
B.3. Changes from version 07 to version 08 . . . . . . . . . . 25 B.3. Changes from version 08 to version 09 . . . . . . . . . . 27
B.4. Changes from version 06 to version 07 . . . . . . . . . . 26 B.4. Changes from version 07 to version 08 . . . . . . . . . . 28
B.5. Changes from version 05 to version 06 . . . . . . . . . . 26 B.5. Changes from version 06 to version 07 . . . . . . . . . . 29
B.6. Changes from version 04 to version 05 . . . . . . . . . . 26 B.6. Changes from version 05 to version 06 . . . . . . . . . . 29
B.7. Changes from version 03 to version 04 . . . . . . . . . . 27 B.7. Changes from version 04 to version 05 . . . . . . . . . . 29
B.8. Changes from version 02 to version 03 . . . . . . . . . . 27 B.8. Changes from version 03 to version 04 . . . . . . . . . . 29
Appendix C. Contributors . . . . . . . . . . . . . . . . . . . . 27 B.9. Changes from version 02 to version 03 . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 Appendix C. Contributors . . . . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30
1. Introduction 1. Introduction
RPL (Routing Protocol for Low-Power and Lossy Networks) [RFC6550] is Routing Protocol for Low-Power and Lossy Networks (RPL) [RFC6550] is
an IPv6 distance vector routing protocol designed to support multiple an IPv6 distance vector routing protocol designed to support multiple
traffic flows through a root-based Destination-Oriented Directed traffic flows through a root-based Destination-Oriented Directed
Acyclic Graph (DODAG). Typically, a router does not have routing Acyclic Graph (DODAG). Typically, a router does not have routing
information for most other routers. Consequently, for traffic information for most other routers. Consequently, for traffic
between routers within the DODAG (i.e., Point-to-Point (P2P) traffic) between routers within the DODAG (i.e., Peer-to-Peer (P2P) traffic)
data packets either have to traverse the root in non-storing mode, or data packets either have to traverse the root in non-storing mode, or
traverse a common ancestor in storing mode. Such P2P traffic is traverse a common ancestor in storing mode. Such P2P traffic is
thereby likely to traverse longer routes and may suffer severe thereby likely to traverse longer routes and may suffer severe
congestion near the root (for more information see [RFC6997], congestion near the root (for more information see [RFC6997],
[RFC6998]). [RFC6998]). The network environment that is considered in this
document is assumed to be the same as described in Section 1 of
[RFC6550].
The route discovery process in AODV-RPL is modeled on the analogous The route discovery process in AODV-RPL is modeled on the analogous
procedure specified in AODV [RFC3561]. The on-demand nature of AODV procedure specified in AODV [RFC3561]. The on-demand nature of AODV
route discovery is natural for the needs of peer-to-peer routing in route discovery is natural for the needs of peer-to-peer routing in
RPL-based LLNs. AODV terminology has been adapted for use with AODV- RPL-based LLNs. AODV terminology has been adapted for use with AODV-
RPL messages, namely RREQ for Route Request, and RREP for Route RPL messages, namely RREQ for Route Request, and RREP for Route
Reply. AODV-RPL currently omits some features compared to AODV -- in Reply. AODV-RPL currently omits some features compared to AODV -- in
particular, flagging Route Errors, blacklisting unidirectional links, particular, flagging Route Errors, "blacklisting" unidirectional
multihoming, and handling unnumbered interfaces. links ([RFC3561]), multihoming, and handling unnumbered interfaces.
AODV-RPL reuses and provides a natural extension to the core RPL AODV-RPL reuses and extends the core RPL functionality to support
functionality to support routes with birectional asymmetric links. routes with bidirectional asymmetric links. It retains RPL's DODAG
It retains RPL's DODAG formation, RPL Instance and the associated formation, RPL Instance and the associated Objective Function
Objective Function (defined in [RFC6551]), trickle timers, and (defined in [RFC6551]), trickle timers, and support for storing and
support for storing and non-storing modes. AODV adds basic messages non-storing modes. AODV-RPL adds basic messages RREQ and RREP as
RREQ and RREP as part of RPL DIO (DODAG Information Object) control part of RPL DODAG Information Object (DIO) control message, which go
messages, and does not utilize the Destination Advertisement Object in separate (paired) RPL instances. AODV-RPL does not utilize the
(DAO) message of RPL. AODV-RPL specifies a new MOP (Mode of Destination Advertisement Object (DAO) control message of RPL. AODV-
Operation) running in a separate instance dedicated to discover P2P RPL specifies a new Mode of Operation (MOP) running in a separate
routes, which may differ from the point-to-multipoint routes instance dedicated to discover P2P routes, which may differ from
discoverable by native RPL. AODV-RPL can be operated whether or not routes discoverable by native RPL. AODV-RPL can be operated whether
native RPL is running otherwise. or not native RPL is running otherwise.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
AODV-RPL reuses names for messages and data structures, including
Rank, DODAG and DODAGID, as defined in RPL [RFC6550].
AODV AODV
Ad Hoc On-demand Distance Vector Routing[RFC3561]. Ad Hoc On-demand Distance Vector Routing[RFC3561].
AODV-RPL Instance
Either the RREQ-Instance or RREP-Instance
Asymmetric Route Asymmetric Route
The route from the OrigNode to the TargNode can traverse different The route from the OrigNode to the TargNode can traverse different
nodes than the route from the TargNode to the OrigNode. An nodes than the route from the TargNode to the OrigNode. An
asymmetric route may result from the asymmetry of links, such that asymmetric route may result from the asymmetry of links, such that
only one direction of the series of links satisfies the Objective only one direction of the series of links satisfies the Objective
Function during route discovery. Function during route discovery.
Bi-directional Asymmetric Link Bi-directional Asymmetric Link
A link that can be used in both directions but with different link A link that can be used in both directions but with different link
characteristics. characteristics.
skipping to change at page 5, line 17 skipping to change at page 5, line 17
OrigNode OrigNode
The IPv6 router (Originating Node) initiating the AODV-RPL route The IPv6 router (Originating Node) initiating the AODV-RPL route
discovery to obtain a route to TargNode. discovery to obtain a route to TargNode.
Paired DODAGs Paired DODAGs
Two DODAGs for a single route discovery process between OrigNode Two DODAGs for a single route discovery process between OrigNode
and TargNode. and TargNode.
P2P P2P
Point-to-Point -- in other words, not constrained a priori to Peer-to-Peer -- in other words, not constrained a priori to
traverse a common ancestor. traverse a common ancestor.
reactive routing reactive routing
Same as "on-demand" routing. Same as "on-demand" routing.
RREQ-DIO message RREQ-DIO message
An AODV-RPL MOP DIO message containing the RREQ option. The An AODV-RPL MOP DIO message containing the RREQ option. The
RPLInstanceID in RREQ-DIO is assigned locally by the OrigNode. RPLInstanceID in RREQ-DIO is assigned locally by the OrigNode.
The RREQ-DIO message has a secure variant as noted in [RFC6550]. The RREQ-DIO message has a secure variant as noted in [RFC6550].
RREP-DIO message RREP-DIO message
An AODV-RPL MOP DIO message containing the RREP option. The An AODV-RPL MOP DIO message containing the RREP option. The
RPLInstanceID in RREP-DIO is typically paired to the one in the RPLInstanceID in RREP-DIO MUST be paired to the one in the
associated RREQ-DIO message. The RREP-DIO message has a secure associated RREQ-DIO message as described in Section 6.3.2. The
variant as noted in [RFC6550]. RREP-DIO message has a secure variant as noted in [RFC6550].
Source routing Source routing
A mechanism by which the source supplies the complete route A mechanism by which the source supplies the complete route
towards the target node along with each data packet [RFC6550]. towards the target node along with each data packet [RFC6550].
Symmetric route Symmetric route
The upstream and downstream routes traverse the same routers. The upstream and downstream routes traverse the same routers and
over the same links.
TargNode TargNode
The IPv6 router (Target Node) for which OrigNode requires a route The IPv6 router (Target Node) for which OrigNode requires a route
and initiates Route Discovery within the LLN network. and initiates Route Discovery within the LLN network.
Upward Direction Upward Direction
The direction from the TargNode to the OrigNode. The direction from the TargNode to the OrigNode.
Upward Route Upward Route
A route in the upward direction. A route in the upward direction.
skipping to change at page 6, line 29 skipping to change at page 6, line 30
AODV-RPL also enables symmetric route discovery along Paired DODAGs AODV-RPL also enables symmetric route discovery along Paired DODAGs
(see Section 5). (see Section 5).
In AODV-RPL, routes are discovered by first forming a temporary DAG In AODV-RPL, routes are discovered by first forming a temporary DAG
rooted at the OrigNode. Paired DODAGs (Instances) are constructed rooted at the OrigNode. Paired DODAGs (Instances) are constructed
according to the AODV-RPL Mode of Operation (MOP) during route according to the AODV-RPL Mode of Operation (MOP) during route
formation between the OrigNode and TargNode. The RREQ-Instance is formation between the OrigNode and TargNode. The RREQ-Instance is
formed by route control messages from OrigNode to TargNode whereas formed by route control messages from OrigNode to TargNode whereas
the RREP-Instance is formed by route control messages from TargNode the RREP-Instance is formed by route control messages from TargNode
to OrigNode. Intermediate routers join the Paired DODAGs based on to OrigNode. Intermediate routers join the Paired DODAGs based on
the Rank as calculated from the DIO message. Henceforth in this the Rank [RFC6550] as calculated from the DIO message. Henceforth in
document, the RREQ-DIO message means the AODV-RPL mode DIO message this document, the RREQ-DIO message means the AODV-RPL mode DIO
from OrigNode to TargNode, containing the RREQ option (see message from OrigNode to TargNode, containing the RREQ option (see
Section 4.1). Similarly, the RREP-DIO message means the AODV-RPL Section 4.1). Similarly, the RREP-DIO message means the AODV-RPL
mode DIO message from TargNode to OrigNode, containing the RREP mode DIO message from TargNode to OrigNode, containing the RREP
option (see Section 4.2). The route discovered in the RREQ-Instance option (see Section 4.2). The route discovered in the RREQ-Instance
is used for transmitting data from TargNode to OrigNode, and the is used for transmitting data from TargNode to OrigNode, and the
route discovered in RREP-Instance is used for transmitting data from route discovered in RREP-Instance is used for transmitting data from
OrigNode to TargNode. OrigNode to TargNode.
4. AODV-RPL DIO Options 4. AODV-RPL DIO Options
4.1. AODV-RPL RREQ Option 4.1. AODV-RPL RREQ Option
OrigNode sets its IPv6 address in the DODAGID field of the RREQ-DIO OrigNode selects one of its IPv6 addresses and sets it in the DODAGID
message. A RREQ-DIO message MUST carry exactly one RREQ option, field of the RREQ-DIO message. Exactly one RREQ option MUST be
otherwise it MUST be dropped. present in a RREQ-DIO message, otherwise the message MUST be dropped.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length |S|H|X| Compr | L | MaxRank | | Option Type | Option Length |S|H|X| Compr | L | MaxRank |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Orig SeqNo | | | Orig SeqNo | |
+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+ |
| | | |
| | | |
skipping to change at page 7, line 33 skipping to change at page 7, line 33
Option Type Option Type
TBD2 TBD2
Option Length Option Length
The length of the option in octets, excluding the Type and Length The length of the option in octets, excluding the Type and Length
fields. Variable due to the presence of the address vector and fields. Variable due to the presence of the address vector and
the number of octets elided according to the Compr value. the number of octets elided according to the Compr value.
S S
Symmetric bit indicating a symmetric route from the OrigNode to Symmetric bit indicating a symmetric route from the OrigNode to
the router transmitting this RREQ-DIO. the router transmitting this RREQ-DIO. See Section 5.
H H
Set to one for a hop-by-hop route. Set to zero for a source Set to one for a hop-by-hop route. Set to zero for a source
route. This flag controls both the downstream route and upstream route. This flag controls both the downstream route and upstream
route. route.
X X
Reserved. Reserved. MUST be set to zero.
Compr Compr
4-bit unsigned integer. Number of prefix octets that are elided 4-bit unsigned integer. Number of prefix octets that are elided
from the Address Vector. The octets elided are shared with the from the Address Vector. The octets elided are shared with the
IPv6 address in the DODAGID. This field is only used in source IPv6 address in the DODAGID. This field is only used in source
routing mode (H=0). In hop-by-hop mode (H=1), this field MUST be routing mode (H=0). In hop-by-hop mode (H=1), this field MUST be
set to zero and ignored upon reception. set to zero and ignored upon reception.
L L
2-bit unsigned integer determining the duration that a node is 2-bit unsigned integer determining the length of time that a node
able to belong to the temporary DAG in RREQ-Instance, including is able to belong to the RREQ-Instance (a temporary DAG including
the OrigNode and the TargNode. Once the time is reached, a node the OrigNode and the TargNode). Once the time is reached, a node
MUST leave the DAG and stop sending or receiving any more DIOs for MUST leave the RREQ-Instance and stop sending or receiving any
the temporary DODAG. more DIOs for the RREQ-Instance. This naturally depends on the
node's ability to keep track of the time.
* 0x00: No time limit imposed. * 0x00: No time limit imposed.
* 0x01: 16 seconds * 0x01: 16 seconds
* 0x02: 64 seconds * 0x02: 64 seconds
* 0x03: 256 seconds * 0x03: 256 seconds
L is independent from the route lifetime, which is defined in the L is independent from the route lifetime, which is defined in the
DODAG configuration option. DODAG configuration option.
MaxRank MaxRank
skipping to change at page 8, line 32 skipping to change at page 8, line 33
Orig SeqNo Orig SeqNo
Sequence Number of OrigNode. See Section 6.1. Sequence Number of OrigNode. See Section 6.1.
Address Vector Address Vector
A vector of IPv6 addresses representing the route that the RREQ- A vector of IPv6 addresses representing the route that the RREQ-
DIO has passed. It is only present when the H bit is set to 0. DIO has passed. It is only present when the H bit is set to 0.
The prefix of each address is elided according to the Compr field. The prefix of each address is elided according to the Compr field.
TargNode can join the RREQ instance at a Rank whose integer portion TargNode can join the RREQ instance at a Rank whose integer portion
is equal to the MaxRank. Other nodes MUST NOT join a RREQ instance is less than or equal to the MaxRank. Other nodes MUST NOT join a
if its own Rank would be equal to or higher than MaxRank. A router RREQ instance if its own Rank would be equal to or higher than
MUST discard a received RREQ if the integer part of the advertised MaxRank. A router MUST discard a received RREQ if the integer part
Rank equals or exceeds the MaxRank limit. of the advertised Rank equals or exceeds the MaxRank limit.
4.2. AODV-RPL RREP Option 4.2. AODV-RPL RREP Option
TargNode sets its IPv6 address in the DODAGID field of the RREP-DIO TargNode sets one of its IPv6 addresses in the DODAGID field of the
message. A RREP-DIO message MUST carry exactly one RREP option, RREP-DIO message. Exactly one RREP option MUST be present in a RREP-
otherwise the message MUST be dropped. TargNode supplies the DIO message, otherwise the message MUST be dropped. TargNode
following information in the RREP option: supplies the following information in the RREP option:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length |G|H|X| Compr | L | MaxRank | | Option Type | Option Length |G|H|X| Compr | L | MaxRank |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Shift |Rsv| | | Shift |X X| |
+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+ |
| | | |
| | | |
| Address Vector (Optional, Variable Length) | | Address Vector (Optional, Variable Length) |
. . . .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Format for AODV-RPL RREP option Figure 2: Format for AODV-RPL RREP option
skipping to change at page 9, line 33 skipping to change at page 9, line 33
Option Length Option Length
The length of the option in octets, excluding the Type and Length The length of the option in octets, excluding the Type and Length
fields. Variable due to the presence of the address vector and fields. Variable due to the presence of the address vector and
the number of octets elided according to the Compr value. the number of octets elided according to the Compr value.
G G
Gratuitous route (see Section 7). Gratuitous route (see Section 7).
H H
Requests either source routing (H=0) or hop-by-hop (H=1) for the The H bit in the RREP option MUST be set to be the same as the H
downstream route. It MUST be set to be the same as the H bit in bit in RREQ option. It requests either source routing (H=0) or
RREQ option. hop-by-hop (H=1) for the downstream route.
X X
Reserved. Reserved. MUST be set to zero.
Compr Compr
4-bit unsigned integer. Same definition as in RREQ option. 4-bit unsigned integer. Same definition as in RREQ option.
L L
2-bit unsigned integer defined as in RREQ option. 2-bit unsigned integer defined as in RREQ option.
MaxRank MaxRank
Similarly to MaxRank in the RREQ message, this field indicates the Similarly to MaxRank in the RREQ message, this field indicates the
upper limit on the integer portion of the Rank. A value of 0 in upper limit on the integer portion of the Rank. A value of 0 in
this field indicates the limit is infinity. this field indicates the limit is infinity.
Shift Shift
6-bit unsigned integer. This field is used to recover the 6-bit unsigned integer. This field is used to recover the
original RPLInstanceID (see Section 6.3.3); 0 indicates that the original RPLInstanceID (see Section 6.3.3); 0 indicates that the
original RPLInstanceID is used. original RPLInstanceID is used.
Rsv X X
MUST be initialized to zero and ignored upon reception. MUST be initialized to zero and ignored upon reception.
Address Vector Address Vector
Only present when the H bit is set to 0. For an asymmetric route, Only present when the H bit is set to 0. For an asymmetric route,
the Address Vector represents the IPv6 addresses of the route that the Address Vector represents the IPv6 addresses of the path
the RREP-DIO has passed. For a symmetric route, it is the Address through the network the RREP-DIO has passed. For a symmetric
Vector when the RREQ-DIO arrives at the TargNode, unchanged during route, it is the Address Vector when the RREQ-DIO arrives at the
the transmission to the OrigNode. TargNode, unchanged during the transmission to the OrigNode.
4.3. AODV-RPL Target Option 4.3. AODV-RPL Target Option
The AODV-RPL Target (ART) Option is based on the Target Option in The AODV-RPL Target (ART) Option is based on the Target Option in
core RPL [RFC6550]. The Flags field is replaced by the Destination core RPL [RFC6550]. The Flags field is replaced by the Destination
Sequence Number of the TargNode and the Prefix Length field is Sequence Number of the TargNode and the Prefix Length field is
reduced to 7 bits so that the value is limited to be no greater than reduced to 7 bits so that the value is limited to be no greater than
127. 127.
A RREQ-DIO message MUST carry at least one ART Option. A RREP-DIO A RREQ-DIO message MUST carry at least one ART Option. A RREP-DIO
skipping to change at page 11, line 11 skipping to change at page 11, line 11
Option Type Option Type
TBD4 TBD4
Option Length Option Length
Length of the option in octets excluding the Type and Length Length of the option in octets excluding the Type and Length
fields. fields.
Dest SeqNo Dest SeqNo
In RREQ-DIO, if nonzero, it is the last known Sequence Number for In RREQ-DIO, if nonzero, it is the Sequence Number for the last
TargNode for which a route is desired. In RREP-DIO, it is the route that OrigNode stored to the TargNode for which a route is
destination sequence number associated to the route. desired. In RREP-DIO, it is the destination sequence number
associated to the route. Zero is used if there is no known
information about the sequence number of TargNode, and not used
otherwise.
r X
A one-bit reserved field. This field MUST be initialized to zero A one-bit reserved field. This field MUST be initialized to zero
by the sender and MUST be ignored by the receiver. by the sender and MUST be ignored by the receiver.
Prefix Length Prefix Length
7-bit unsigned integer. Number of valid leading bits in the IPv6 7-bit unsigned integer. Number of valid leading bits in the IPv6
Prefix. If Prefix Length is 0, then the value in the Target Prefix. If Prefix Length is 0, then the value in the Target
Prefix / Address field represents an IPv6 address, not a prefix. Prefix / Address field represents an IPv6 address, not a prefix.
Target Prefix / Address Target Prefix / Address
(variable-length field) An IPv6 destination address or prefix. (variable-length field) An IPv6 destination address or prefix.
The Prefix Length field contains the number of valid leading bits The Prefix Length field contains the number of valid leading bits
in the prefix. The length of the field is the least number of in the prefix. The Target Prefix / Address field contains the
octets that can contain all of the bits of the Prefix, in other least number of octets that can represent all of the bits of the
words Floor((7+(Prefix Length))/8) octets. The remaining bits in Prefix, in other words Ceil(Prefix Length/8) octets. The initial
the Target Prefix / Address field after the prefix length (if any) bits in the Target Prefix / Address field preceding the prefix
MUST be set to zero on transmission and MUST be ignored on length (if any) MUST be set to zero on transmission and MUST be
receipt. ignored on receipt. If Prefix Length is zero, the Address field
is 128 bits for IPv6 addresses.
5. Symmetric and Asymmetric Routes 5. Symmetric and Asymmetric Routes
Links are considered symmetric until additional information is Links are considered symmetric until indication to the contrary is
collected. In Figure 4 and Figure 5, BR is the Border Router, O is received. In Figure 4 and Figure 5, BR is the Border Router, O is
the OrigNode, R is an intermediate router, and T is the TargNode. If the OrigNode, each R is an intermediate router, and T is the
the RREQ-DIO arrives over an interface that is known to be symmetric, TargNode. If the RREQ-DIO arrives over an interface that is known to
and the S bit is set to 1, then it remains as 1, as illustrated in be symmetric, and the S bit is set to 1, then it remains as 1, as
Figure 4. If an intermediate router sends out RREQ-DIO with the S illustrated in Figure 4. If an intermediate router sends out RREQ-
bit set to 1, then all the one-hop links on the route from the DIO with the S bit set to 1, then each link en route from the
OrigNode O to this router meet the requirements of route discovery, OrigNode O to this router has met the requirements of route
and the route can be used symmetrically. discovery, and the route can be used symmetrically.
BR BR
/----+----\ /----+----\
/ | \ / | \
/ | \ / | \
R R R R R R
_/ \ | / \ _/ \ | / \
/ \ | / \ / \ | / \
/ \ | / \ / \ | / \
R -------- R --- R ----- R -------- R R -------- R --- R ----- R -------- R
skipping to change at page 12, line 29 skipping to change at page 12, line 29
/ \ / \ / \ / \ / \ / \ / \ / \
/ \ / \ / \ / \ / \ / \ / \ / \
R ----- R ----------- R ----- R ----- R ----- R ---- R----- R R ----- R ----------- R ----- R ----- R ----- R ---- R----- R
>---- RREQ-Instance (Control: O-->T; Data: T-->O) -------> >---- RREQ-Instance (Control: O-->T; Data: T-->O) ------->
<---- RREP-Instance (Control: T-->O; Data: O-->T) -------< <---- RREP-Instance (Control: T-->O; Data: O-->T) -------<
Figure 4: AODV-RPL with Symmetric Paired Instances Figure 4: AODV-RPL with Symmetric Paired Instances
Upon receiving a RREQ-DIO with the S bit set to 1, a node determines Upon receiving a RREQ-DIO with the S bit set to 1, a node determines
whether this one-hop link can be used symmetrically, i.e., both the whether this link can be used symmetrically, i.e., both directions
two directions meet the requirements of data transmission. If the meet the requirements of data transmission. If the RREQ-DIO arrives
RREQ-DIO arrives over an interface that is not known to be symmetric, over an interface that is not known to be symmetric, or is known to
or is known to be asymmetric, the S bit is set to 0. If the S bit be asymmetric, the S bit is set to 0. If the S bit arrives already
arrives already set to be '0', it is set to be '0' on retransmission set to be '0', it is set to be '0' when the RREQ-DIO is propagated
(Figure 5). For an asymmetric route, there is at least one hop which (Figure 5). For an asymmetric route, there is at least one hop which
doesn't satisfy the Objective Function. Based on the S bit received doesn't satisfy the Objective Function. Based on the S bit received
in RREQ-DIO, TargNode T determines whether or not the route is in RREQ-DIO, TargNode T determines whether or not the route is
symmetric before transmitting the RREP-DIO message upstream towards symmetric before transmitting the RREP-DIO message upstream towards
the OrigNode O. the OrigNode O.
The criteria used to determine whether or not each link is symmetric The criteria used to determine whether or not each link is symmetric
is beyond the scope of the document. For instance, intermediate is beyond the scope of the document. For instance, intermediate
routers can use local information (e.g., bit rate, bandwidth, number routers can use local information (e.g., bit rate, bandwidth, number
of cells used in 6tisch), a priori knowledge (e.g. link quality of cells used in 6tisch [RFC9030]), a priori knowledge (e.g., link
according to previous communication) or use averaging techniques as quality according to previous communication) or use averaging
appropriate to the application. Other link metric information can be techniques as appropriate to the application. Other link metric
acquired before AODV-RPL operation, by executing evaluation information can be acquired before AODV-RPL operation, by executing
procedures; for instance test traffic can be generated between nodes evaluation procedures; for instance test traffic can be generated
of the deployed network. During AODV-RPL operation, OAM techniques between nodes of the deployed network. During AODV-RPL operation,
for evaluating link state (see([RFC7548], [RFC7276], [co-ioam]) MAY OAM techniques for evaluating link state (see [RFC7548], [RFC7276],
be used (at regular intervals appropriate for the LLN). The [co-ioam]) MAY be used (at regular intervals appropriate for the
evaluation procedures are out of scope for AODV-RPL. LLN). The evaluation procedures are out of scope for AODV-RPL.
Appendix A describes an example method using the upstream Expected Appendix A describes an example method using the upstream Expected
Number of Transmissions" (ETX) and downstream Received Signal Number of Transmissions (ETX) and downstream Received Signal Strength
Strength Indicator (RSSI) to estimate whether the link is symmetric Indicator (RSSI) to estimate whether the link is symmetric in terms
in terms of link quality is given in using an averaging technique. of link quality using an averaging technique.
BR BR
/----+----\ /----+----\
/ | \ / | \
/ | \ / | \
R R R R R R
/ \ | / \ / \ | / \
/ \ | / \ / \ | / \
/ \ | / \ / \ | / \
R --------- R --- R ---- R --------- R R --------- R --- R ---- R --------- R
skipping to change at page 13, line 34 skipping to change at page 13, line 34
/ <--S=0-- / \ / \ / <--S=0-- / <--S=0-- / \ / \ / <--S=0--
/ \ / \ / \ / \ / \ / \ / \ / \
R ----- R ----------- R ----- R ----- R ----- R ---- R----- R R ----- R ----------- R ----- R ----- R ----- R ---- R----- R
<--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0--
>---- RREQ-Instance (Control: O-->T; Data: T-->O) -------> >---- RREQ-Instance (Control: O-->T; Data: T-->O) ------->
<---- RREP-Instance (Control: T-->O; Data: O-->T) -------< <---- RREP-Instance (Control: T-->O; Data: O-->T) -------<
Figure 5: AODV-RPL with Asymmetric Paired Instances Figure 5: AODV-RPL with Asymmetric Paired Instances
As illustrated in Figure 5, an intermediate router determines the S
bit value that the RREQ-DIO should carry using link asymmetry
detection methods as discussed earlier in this section. In many
cases the intermediate router has already made the link asymmetry
decision by the time RREQ-DIO arrives.
6. AODV-RPL Operation 6. AODV-RPL Operation
6.1. Route Request Generation 6.1. Route Request Generation
The route discovery process is initiated when an application at the The route discovery process is initiated when an application at the
OrigNode has data to be transmitted to the TargNode, but does not OrigNode has data to be transmitted to the TargNode, but does not
have a route that satisfies the Objective Function for the target of have a route that satisfies the Objective Function for the target of
the data transmission. In this case, the OrigNode builds a local the data transmission. In this case, the OrigNode builds a local
RPLInstance and a DODAG rooted at itself. Then it transmits a DIO RPLInstance and a DODAG rooted at itself. Then it transmits a DIO
message containing exactly one RREQ option (see Section 4.1) via message containing exactly one RREQ option (see Section 4.1) via
link-local multicast. The DIO MUST contain at least one ART Option link-local multicast. The DIO MUST contain at least one ART Option
(see Section 4.3). The S bit in RREQ-DIO sent out by the OrigNode is (see Section 4.3). The required ART Option indicates the TargNode.
set to 1. The S bit in RREQ-DIO sent out by the OrigNode is set to 1.
Each node maintains a sequence number; the operation is specified in Each node maintains a sequence number; the operation is specified in
section 7.2 of [RFC6550]. When the OrigNode initiates a route section 7.2 of [RFC6550]. When the OrigNode initiates a route
discovery process, it MUST increase its own sequence number to avoid discovery process, it MUST increase its own sequence number to avoid
conflicts with previously established routes. The sequence number is conflicts with previously established routes. The sequence number is
carried in the Orig SeqNo field of the RREQ option. carried in the Orig SeqNo field of the RREQ option.
The address in the ART Option can be a unicast IPv6 address or a The address in the ART Option can be a unicast IPv6 address or a
prefix. The OrigNode can initiate the route discovery process for prefix. The OrigNode can initiate the route discovery process for
multiple targets simultaneously by including multiple ART Options, multiple targets simultaneously by including multiple ART Options.
and within a RREQ-DIO the requirements for the routes to different Within a RREQ-DIO the requirements for the routes to different
TargNodes MUST be the same. TargNodes MUST be the same.
OrigNode can maintain different RPLInstances to discover routes with OrigNode can maintain different RPLInstances to discover routes with
different requirements to the same targets. Using the RPLInstanceID different requirements to the same targets. Using the RPLInstanceID
pairing mechanism (see Section 6.3.3), route replies (RREP-DIOs) for pairing mechanism (see Section 6.3.3), route replies (RREP-DIOs) for
different RPLInstances can be distinguished. different RPLInstances can be generated.
The transmission of RREQ-DIO obeys the Trickle timer [RFC6206]. If The transmission of RREQ-DIO obeys the Trickle timer [RFC6206]. If
the duration specified by the L bit has elapsed, the OrigNode MUST the length of time specified by the L field has elapsed, the OrigNode
leave the DODAG and stop sending RREQ-DIOs in the related MUST leave the DODAG and stop sending RREQ-DIOs in the related
RPLInstance. RPLInstance.
6.2. Receiving and Forwarding RREQ messages 6.2. Receiving and Forwarding RREQ messages
6.2.1. General Processing 6.2.1. General Processing
Upon receiving a RREQ-DIO, a router goes through the steps below. If Upon receiving a RREQ-DIO, a router goes through the steps below. If
the router does not belong to the RREQ-Instance, then the maximum the router has not joined the RREQ-Instance, then the maximum useful
useful rank (MaxUseRank) is MaxRank. Otherwise, MaxUseRank is set to rank (MaxUseRank) is MaxRank. Otherwise, MaxUseRank is set to be the
be the Rank value that was stored when the router processed the best Rank value that was stored when the router processed the best
previous RREQ for the DODAG with the given RREQ-Instance. previous RREQ for the DODAG with the given RREQ-Instance.
Step 1: Step 1:
If the S bit in the received RREQ-DIO is set to 1, the router MUST The router MUST first determine whether to propagate the RREQ-DIO.
determine whether each direction of the link (by which the RREQ- It does this by determining whether or not the downstream
DIO is received) satisfies the Objective Function. In case that direction of the incoming link satisfies the Objective Function
the downward (i.e. towards the TargNode) direction of the link (OF). If not the RREQ-DIO MUST be dropped, and the following
does not satisfy the Objective Function, the link can't be used steps are not processed. Otherwise, the router MUST join the
symmetrically, thus the S bit of the RREQ-DIO to be sent out MUST RREQ-Instance and prepare to propagate the RREQ-DIO. The upstream
be set as 0. If the S bit in the received RREQ-DIO is set to 0, neighbor router that transmitted the received RREQ-DIO is selected
the router MUST determine into the upward direction (towards the as the preferred parent.
OrigNode) of the link.
If the upward direction of the link can satisfy the Objective
Function, and the router's Rank would not exceed the MaxUseRank
limit, the router joins the DODAG of the RREQ-Instance. The
router that transmitted the received RREQ-DIO is selected as the
preferred parent. Otherwise, if the Objective Function is not
satisfied or the MaxUseRank limit is exceeded, the router MUST
discard the received RREQ-DIO and MUST NOT join the DODAG.
Step 2: Step 2:
Then the router checks if one of its addresses is included in one
of the ART Options. If so, this router is one of the TargNodes.
Otherwise, it is an intermediate router.
Step 3:
If the H bit is set to 1, then the router (TargNode or If the H bit is set to 1, then the router (TargNode or
intermediate) MUST build an upward route entry towards OrigNode intermediate) MUST build an upward route entry towards OrigNode
which includes at least the following items: Source Address, which includes at least the following items: Source Address,
RPLInstanceID, Destination Address, Next Hop, Lifetime, and RPLInstanceID, Destination Address, Next Hop, Lifetime, and
Sequence Number. The Destination Address and the RPLInstanceID Sequence Number. The Destination Address and the RPLInstanceID
respectively can be learned from the DODAGID and the RPLInstanceID respectively can be learned from the DODAGID and the RPLInstanceID
of the RREQ-DIO, and the Source Address is the address used by the of the RREQ-DIO, and the Source Address is the address used by the
local router to send data to the OrigNode. The Next Hop is the local router to send data to the Next Hop, i.e., the preferred
preferred parent. The lifetime is set according to DODAG parent. The lifetime is set according to DODAG configuration (not
configuration (i.e., not the L bit) and can be extended when the the L field) and can be extended when the route is actually used.
route is actually used. The sequence number represents the The sequence number represents the freshness of the route entry,
freshness of the route entry, and it is copied from the Orig SeqNo and it is copied from the Orig SeqNo field of the RREQ option. A
field of the RREQ option. A route entry with the same source and route entry with the same source and destination address, same
destination address, same RPLInstanceID, but stale sequence RPLInstanceID, but stale sequence number, MUST be deleted.
number, MUST be deleted.
Step 3:
If the S bit of the incoming RREQ-DIO is 0, then the route cannot
be symmetric, and the S bit of the RREQ-DIO to be transmitted is
set to 0. Otherwise, the router MUST determine whether the
downward (i.e., towards the TargNode) direction of the incoming
link satisfies the OF. If so, the S bit of the RREQ-DIO to be
transmitted is set to 1. Otherwise the S bit of the RREQ-DIO to
be transmitted is set to 0.
When a router joins the RREQ-Instance, it also associates within
its data structure for the RREQ-Instance the information about
whether or not the RREQ-DIO to be transmitted has the S-bit set to
1. This information associated to RREQ-Instance is known as the
S-bit of the RREQ-Instance. It will be used later during the
RREP-DIO message processing Section 6.3.2 for RPLInstance pairing
as described in Section 6.4.
Step 4: Step 4:
If the router is an intermediate router, then it transmits a RREQ- The router checks whether one of its addresses is included in one
DIO via link-local multicast; if the H bit is set to 0, the of the ART Options. If so, this router is one of the TargNodes.
Otherwise, it is an intermediate router.
If the router is an intermediate router, then it transmits the
RREQ-DIO via link-local multicast; if the H bit is set to 0, the
intermediate router MUST include the address of the interface intermediate router MUST include the address of the interface
receiving the RREQ-DIO into the address vector. Otherwise, if the receiving the RREQ-DIO into the address vector. Otherwise, the
router (i.e., TargNode) was not already associated with the RREQ- router is TargNode; if it was not already associated with the
Instance, it prepares a RREP-DIO (Section 6.3). If, on the other RREQ-Instance, it prepares and transmits a RREP-DIO (Section 6.3).
hand TargNode was already associated with the RREQ-Instance, it If, on the other hand, TargNode was already associated with the
takes no further action and does not send an RREP-DIO. RREQ-Instance, it takes no further action and does not send an
RREP-DIO.
6.2.2. Additional Processing for Multiple Targets 6.2.2. Additional Processing for Multiple Targets
If the OrigNode tries to reach multiple TargNodes in a single RREQ- If the OrigNode tries to reach multiple TargNodes in a single RREQ-
Instance, one of the TargNodes can be an intermediate router to the Instance, one of the TargNodes can be an intermediate router to the
others, therefore it MUST continue sending RREQ-DIO to reach other others, therefore it MUST continue sending RREQ-DIO to reach other
targets. In this case, before rebroadcasting the RREQ-DIO, a targets. In this case, before transmitting the RREQ-DIO via link-
TargNode MUST delete the Target Option encapsulating its own address, local multicast, a TargNode MUST delete the Target Option
so that downstream routers with higher Rank values do not try to encapsulating its own address, so that downstream routers with higher
create a route to this TargNode. Rank values do not try to create a route to this TargNode.
An intermediate router could receive several RREQ-DIOs from routers An intermediate router could receive several RREQ-DIOs from routers
with lower Rank values in the same RREQ-Instance but have different with lower Rank values in the same RREQ-Instance with different lists
lists of Target Options. When rebroadcasting the RREQ-DIO, the of Target Options. When transmitting the RREQ-DIO, the intersection
intersection of these lists MUST be included. For example, suppose of all received lists MUST be included. For example, suppose two
two RREQ-DIOs are received with the same RPLInstance and OrigNode. RREQ-DIOs are received with the same RPLInstance and OrigNode.
Suppose further that the first RREQ has (T1, T2) as the targets, and Suppose further that the first RREQ has (T1, T2) as the targets, and
the second one has (T2, T4) as targets. Then only T2 needs to be the second one has (T2, T4) as targets. Then only T2 needs to be
included in the generated RREQ-DIO. If the intersection is empty, it included in the generated RREQ-DIO. If the intersection is empty, it
means that all the targets have been reached, and the router MUST NOT means that all the targets have been reached, and the router MUST NOT
send out any RREQ-DIO. For the purposes of determining the transmit any RREQ-DIO. For the purposes of determining the
intersection with previous incoming RREQ-DIOs, the intermediate intersection with previous incoming RREQ-DIOs, the intermediate
router maintains a record of the targets that have been requested router maintains a record of the targets that have been requested for
associated with the RREQ-Instance. Any RREQ-DIO message with a given RREQ-Instance. Any incoming RREQ-DIO message having multiple
different ART Options coming from a router with higher Rank is ART Options coming from a router with higher Rank than the Rank of
ignored. the stored targets is ignored.
6.3. Generating Route Reply (RREP) at TargNode 6.3. Generating Route Reply (RREP) at TargNode
When H=1 in the incoming RREQ, the TargNode MUST NOT generate a RREP
if one of its addresses is present in the Address Vector. If the
implementation selects the symmetric route, and the L field is not 0,
the TargNode MAY delay transmitting the RREP-DIO for duration
RREP_WAIT_TIME to await a route with a lower Rank. The value of
RREP_WAIT_TIME is set by default to 1/4 of the duration determined by
the L field. For L == 0, RREP_WAIT_TIME is set by default to 0.
Depending upon the application, RREP_WAIT_TIME may be set to other
values. Smaller values enable quicker formation for the P2P route.
Larger values enable formation of P2P routes with better Rank values.
6.3.1. RREP-DIO for Symmetric route 6.3.1. RREP-DIO for Symmetric route
If a RREQ-DIO arrives at TargNode with the S bit set to 1, there is a If a RREQ-DIO arrives at TargNode with the S bit set to 1, there is a
symmetric route along which both directions satisfy the Objective symmetric route both of whose directions satisfy the Objective
Function. Other RREQ-DIOs might later provide asymmetric upward Function. Other RREQ-DIOs might later provide better upward routes.
routes (i.e. S=0). Selection between a qualified symmetric route The method of selection between a qualified symmetric route and an
and an asymmetric route that might have better performance is asymmetric route that might have better performance is
implementation-specific and out of scope. If the implementation implementation-specific and out of scope.
selects the symmetric route, and the L bit is not 0, the TargNode MAY
delay transmitting the RREP-DIO for duration RREP_WAIT_TIME to await
a symmetric route with a lower Rank. The value of RREP_WAIT_TIME is
set by default to 1/4 of the time duration determined by the L bit.
For a symmetric route, the RREP-DIO message is unicast to the next For a symmetric route, the RREP-DIO message is unicast to the next
hop according to the accumulated address vector (H=0) or the route hop according to the accumulated address vector (H=0) or the route
entry (H=1). Thus the DODAG in RREP-Instance does not need to be entry (H=1). Thus the DODAG in RREP-Instance does not need to be
built. The RPLInstanceID in the RREP-Instance is paired as defined built. The RPLInstanceID in the RREP-Instance is paired as defined
in Section 6.3.3. In case the H bit is set to 0, the address vector in Section 6.3.3. In case the H bit is set to 0, the address vector
received in the RREQ-DIO MUST be included in the RREP-DIO. TargNode received in the RREQ-DIO MUST be included in the RREP-DIO. TargNode
increments its current sequence number and uses the incremented increments its current sequence number and uses the incremented
result in the Dest SeqNo in the ART option of the RREQ-DIO. The result in the Dest SeqNo in the ART option of the RREQ-DIO. The
address of the OrigNode MUST be encapsulated in the ART Option and address of the OrigNode MUST be encapsulated in the ART Option and
included in this RREP-DIO message. included in this RREP-DIO message.
6.3.2. RREP-DIO for Asymmetric Route 6.3.2. RREP-DIO for Asymmetric Route
When a RREQ-DIO arrives at a TargNode with the S bit set to 0, the When a RREQ-DIO arrives at a TargNode with the S bit set to 0, the
TargNode MUST build a DODAG in the RREP-Instance rooted at itself in TargNode MUST build a DODAG in the RREP-Instance corresponding to the
order to discover the downstream route from the OrigNode to the RREQ-DIO, rooted at itself in order to discover the downstream route
TargNode. The RREP-DIO message MUST be re-transmitted via link-local from the OrigNode to the TargNode. The RREP-DIO message MUST be
multicast until the OrigNode is reached or MaxRank is exceeded. The transmitted via link-local multicast until the OrigNode is reached or
TargNode MAY delay transmitting the RREP-DIO for duration MaxRank is exceeded.
RREP_WAIT_TIME to await a route with a lower Rank. The value of
RREP_WAIT_TIME is set by default to 1/4 of the time duration
determined by the L bit.
The settings of the fields in RREP option and ART option are the same The settings of the fields in RREP option and ART option are the same
as for the symmetric route, except for the S bit. as for the symmetric route, except for the value of the S bit
associated with the RREP-instance.
6.3.3. RPLInstanceID Pairing 6.3.3. RPLInstanceID Pairing
Since the RPLInstanceID is assigned locally (i.e., there is no Since the RPLInstanceID is assigned locally (i.e., there is no
coordination between routers in the assignment of RPLInstanceID), the coordination between routers in the assignment of RPLInstanceID), the
tuple (OrigNode, TargNode, RPLInstanceID) is needed to uniquely tuple (OrigNode, TargNode, RPLInstanceID) is needed to uniquely
identify a discovered route. It is possible that multiple route identify a discovered route. It is possible that multiple route
discoveries with dissimilar Objective Functions are initiated discoveries with dissimilar Objective Functions are initiated
simultaneously. Thus between the same pair of OrigNode and TargNode, simultaneously. Thus between the same pair of OrigNode and TargNode,
there can be multiple AODV-RPL route discovery instances. To avoid there can be multiple AODV-RPL route discovery instances. To avoid
any mismatch, the RREQ-Instance and the RREP-Instance in the same any mismatch, the RREQ-Instance and the RREP-Instance in the same
route discovery MUST be paired using the RPLInstanceID. route discovery MUST be paired using the RPLInstanceID.
When preparing the RREP-DIO, a TargNode could find the RPLInstanceID When preparing the RREP-DIO, a TargNode could find the RPLInstanceID
to be used for the RREP-Instance is already occupied by another RPL candidate for the RREP-Instance is already occupied by another RPL
Instance from an earlier route discovery operation which is still Instance from an earlier route discovery operation which is still
active. In other words, it might happen that two distinct OrigNodes active. This unlikely case might happen if two distinct OrigNodes
need routes to the same TargNode, and they happen to use the same need routes to the same TargNode, and they happen to use the same
RPLInstanceID for RREQ-Instance. In this case, the occupied RPLInstanceID for RREQ-Instance. In such cases, the original
RPLInstanceID MUST NOT be used again. Then the second RPLInstanceID RPLInstanceID of an already active RREP-Instance MUST NOT be used
MUST be shifted into another integer so that the two RREP-instances again for assigning RPLInstanceID for the later RREP-Instance.
can be distinguished. In RREP option, the Shift field indicates the Reusing the same RPLInstanceID for two distinct DODAGs originated
shift to be applied to original RPLInstanceID. When the new with the same DODAGID (TargNode address) would prevent intermediate
RPLInstanceID after shifting exceeds 63, it rolls over starting at 0. routers to distinguish between these DODAGs (and their associated
For example, the original RPLInstanceID is 60, and shifted by 6, the Objective Functions). Instead, the RPLInstanceID MUST be replaced by
new RPLInstanceID will be 2. Related operations can be found in another value so that the two RREP-instances can be distinguished.
Section 6.4. In RREP-DIO option, the Shift field of the RREP-DIO message(Figure 2)
indicates the shift to be applied to original RPLInstanceID to obtain
the replacement RPLInstanceID. When the new RPLInstanceID after
shifting exceeds 255, it rolls over starting at 0. For example, if
the original RPLInstanceID is 252, and shifted by 6, the new
RPLInstanceID will be 2. Related operations can be found in
Section 6.4. RPLInstanceID collisions do not occur across RREQ-DIOs;
the DODAGID equals the OrigNode address and is sufficient to
disambiguate between DODAGs.
6.4. Receiving and Forwarding Route Reply 6.4. Receiving and Forwarding Route Reply
Upon receiving a RREP-DIO, a router which does not belong to the Upon receiving a RREP-DIO, a router performs the following steps:
RREQ-Instance goes through the following steps:
Step 1: Step 1:
If the S bit is set to 1, the router MUST proceed to step 2. If the Objective Function is not satisfied, the router MUST NOT
join the DODAG; the router MUST discard the RREQ-DIO, and does not
execute the remaining steps in this section. An Intermediate
Router MUST NOT forward a RREP if one of its addresses is present
in the Address Vector, and does not execute the remaining steps in
this section.
If the S bit of the RREP-DIO is set to 0, the router MUST If the S bit of the associated RREQ-Instance is set to 1, the
router MUST proceed to step 2.
If the S-bit of the RREQ-Instance is set to 0, the router MUST
determine whether the downward direction of the link (towards the determine whether the downward direction of the link (towards the
TargNode) over which the RREP-DIO is received satisfies the TargNode) over which the RREP-DIO is received satisfies the
Objective Function, and the router's Rank would not exceed the Objective Function, and the router's Rank would not exceed the
MaxRank limit. If so, the router joins the DODAG of the RREP- MaxRank limit. If so, the router joins the DODAG of the RREP-
Instance. The router that transmitted the received RREP-DIO is Instance. The router that transmitted the received RREP-DIO is
selected as the preferred parent. Afterwards, other RREP-DIO selected as the preferred parent. Afterwards, other RREP-DIO
messages can be received. messages can be received.
If the Objective Function is not satisfied, the router MUST NOT
join the DODAG; the router MUST discard the RREQ-DIO, and does not
execute the remaining steps in this section.
Step 2: Step 2:
The router next checks if one of its addresses is included in the The router next checks if one of its addresses is included in the
ART Option. If so, this router is the OrigNode of the route ART Option. If so, this router is the OrigNode of the route
discovery. Otherwise, it is an intermediate router. discovery. Otherwise, it is an intermediate router.
Step 3: Step 3:
If the H bit is set to 1, then the router (OrigNode or If the H bit is set to 1, then the router (OrigNode or
intermediate) MUST build a downward route entry towards TargNode intermediate) MUST build a downward route entry towards TargNode
which includes at least the following items: OrigNode Address, which includes at least the following items: OrigNode Address,
RPLInstanceID, TargNode Address as destination, Next Hop, Lifetime RPLInstanceID, TargNode Address as destination, Next Hop, Lifetime
and Sequence Number. For a symmetric route, the Next Hop in the and Sequence Number. For a symmetric route, the Next Hop in the
route entry is the router from which the RREP-DIO is received. route entry is the router from which the RREP-DIO is received.
For an asymmetric route, the Next Hop is the preferred parent in For an asymmetric route, the Next Hop is the preferred parent in
the DODAG of RREQ-Instance. The RPLInstanceID in the route entry the DODAG of RREQ-Instance. The RPLInstanceID in the route entry
MUST be the original RPLInstanceID (after subtracting the Shift MUST be the original RPLInstanceID (after subtracting the Shift
field value). The source address is learned from the ART Option, field value). The source address is learned from the ART Option,
and the destination address is learned from the DODAGID. The and the destination address is learned from the DODAGID. The
lifetime is set according to DODAG configuration (i.e., not the L lifetime is set according to DODAG configuration (i.e., not the L
bit) and can be extended when the route is actually used. The field) and can be extended when the route is actually used. The
sequence number represents the freshness of the route entry, and sequence number represents the freshness of the route entry, and
is copied from the Dest SeqNo field of the ART option of the RREP- is copied from the Dest SeqNo field of the ART option of the RREP-
DIO. A route entry with same source and destination address, same DIO. A route entry with same source and destination address, same
RPLInstanceID, but stale sequence number, MUST be deleted. RPLInstanceID, but stale sequence number (i.e., incoming sequence
number is less than the currently stored sequence number of the
route entry), MUST be deleted.
Step 4: Step 4:
If the receiver is the OrigNode, it can start transmitting the If the receiver is the OrigNode, it can start transmitting the
application data to TargNode along the path as provided in RREP- application data to TargNode along the path as provided in RREP-
Instance, and processing for the RREP-DIO is complete. Otherwise, Instance, and processing for the RREP-DIO is complete. Otherwise,
in case of an asymmetric route, the intermediate router MUST in case of an asymmetric route, the intermediate router MUST
include the address of the interface receiving the RREP-DIO into include the address of the interface receiving the RREP-DIO into
the address vector, and then transmit the RREP-DIO via link-local the address vector, and then transmit the RREP-DIO via link-local
multicast. In case of a symmetric route, the RREP-DIO message is multicast. In case of a symmetric route, the RREP-DIO message is
unicast to the Next Hop according to the address vector in the unicast to the Next Hop according to the address vector in the
RREP-DIO (H=0) or the local route entry (H=1). The RPLInstanceID RREP-DIO (H=0) or the local route entry (H=1). The RPLInstanceID
in the transmitted RREP-DIO is the same as the value in the in the transmitted RREP-DIO is the same as the value in the
received RREP-DIO. The local knowledge for the TargNode's received RREP-DIO. The local knowledge for the TargNode's
sequence number SHOULD be updated. sequence number SHOULD be updated.
Upon receiving a RREP-DIO, a router which already belongs to the Upon receiving a RREP-DIO, a router which already belongs to the
RREQ-Instance SHOULD drop the RREP-DIO. RREP-Instance SHOULD drop the RREP-DIO.
7. Gratuitous RREP 7. Gratuitous RREP
In some cases, an Intermediate router that receives a RREQ-DIO In some cases, an Intermediate router that receives a RREQ-DIO
message MAY transmit a "Gratuitous" RREP-DIO message back to OrigNode message MAY transmit a "Gratuitous" RREP-DIO message back to OrigNode
instead of continuing to multicast the RREQ-DIO towards TargNode. instead of continuing to multicast the RREQ-DIO towards TargNode.
The intermediate router effectively builds the RREP-Instance on The intermediate router effectively builds the RREP-Instance on
behalf of the actual TargNode. The G bit of the RREP option is behalf of the actual TargNode. The G bit of the RREP option is
provided to distinguish the Gratuitous RREP-DIO (G=1) sent by the provided to distinguish the Gratuitous RREP-DIO (G=1) sent by the
Intermediate node from the RREP-DIO sent by TargNode (G=0). Intermediate node from the RREP-DIO sent by TargNode (G=0).
The gratuitous RREP-DIO can be sent out when an intermediate router The gratuitous RREP-DIO can be sent out when an intermediate router
receives a RREQ-DIO for a TargNode, and the router has a more recent receives a RREQ-DIO for a TargNode, and the router has a more recent
(larger destination sequence number) pair of downward and upward (larger destination sequence number) pair of downward and upward
routes to the TargNode which also satisfy the Objective Function. routes to the TargNode which also satisfy the Objective Function.
In case of source routing, the intermediate router MUST unicast the In case of source routing, the intermediate router MUST unicast the
received RREQ-DIO to TargNode including the address vector between received RREQ-DIO to TargNode including the address vector between
the OrigNode and the router. Thus the TargNode can have a complete the OrigNode and the router. Thus the TargNode can have a complete
upward route address vector from itself to the OrigNode. Then the upward route address vector from itself to the OrigNode. Then the
router MUST send out the gratuitous RREP-DIO including the address router MUST transmit the gratuitous RREP-DIO including the address
vector from the router itself to the TargNode. vector from the router itself to the TargNode.
In case of hop-by-hop routing, the intermediate router MUST unicast In case of hop-by-hop routing, the intermediate router MUST unicast
the received RREQ-DIO to the Next Hop on the route. The Next Hop the received RREQ-DIO to the Next Hop on the route. The Next Hop
router along the route MUST build new route entries with the related router along the route MUST build new route entries with the related
RPLInstanceID and DODAGID in the downward direction. The above RPLInstanceID and DODAGID in the downward direction. The above
process will happen recursively until the RREQ-DIO arrives at the process will happen recursively until the RREQ-DIO arrives at the
TargNode. Then the TargNode MUST unicast recursively the RREP-DIO TargNode. Then the TargNode MUST unicast recursively the RREP-DIO
hop-by-hop to the intermediate router, and the routers along the hop-by-hop to the intermediate router, and the routers along the
route SHOULD build new route entries in the upward direction. Upon route SHOULD build new route entries in the upward direction. Upon
skipping to change at page 20, line 5 skipping to change at page 20, line 39
"DIO Transmission". "DIO Transmission".
9. IANA Considerations 9. IANA Considerations
Note to RFC editor: Note to RFC editor:
The sentences "The parenthesized number 5 is only a suggestion." and The sentences "The parenthesized number 5 is only a suggestion." and
"The parenthesized numbers are only suggestions." are to be removed "The parenthesized numbers are only suggestions." are to be removed
prior publication. prior publication.
A Subregistry in this section refers to a named sub-registry of the
"Routing Protocol for Low Power and Lossy Networks (RPL)" registry.
9.1. New Mode of Operation: AODV-RPL 9.1. New Mode of Operation: AODV-RPL
IANA is asked to assign a new Mode of Operation, named "AODV-RPL" for IANA is asked to assign a new Mode of Operation, named "AODV-RPL" for
Point-to-Point(P2P) hop-by-hop routing from the "Mode of Operation" peer-to-peer hop-by-hop routing from the "Mode of Operation"
Registry. The parenthesized number 5 is only a suggestion. Subregistry. The parenthesized number 5 is only a suggestion.
+-------------+---------------+---------------+ +-------------+---------------+---------------+
| Value | Description | Reference | | Value | Description | Reference |
+-------------+---------------+---------------+ +-------------+---------------+---------------+
| TBD1 (5) | AODV-RPL | This document | | TBD1 (5) | AODV-RPL | This document |
+-------------+---------------+---------------+ +-------------+---------------+---------------+
Figure 6: Mode of Operation Figure 6: Mode of Operation
9.2. AODV-RPL Options: RREQ, RREP, and Target 9.2. AODV-RPL Options: RREQ, RREP, and Target
IANA is asked to assign three new AODV-RPL options "RREQ", "RREP" and IANA is asked to assign three new AODV-RPL options "RREQ", "RREP" and
"ART", as described in Figure 7 from the "RPL Control Message "ART", as described in Figure 7 from the "RPL Control Message
Options" Registry. The parenthesized numbers are only suggestions. Options" Subregistry. The parenthesized numbers are only
suggestions.
+-------------+------------------------+---------------+ +-------------+------------------------+---------------+
| Value | Meaning | Reference | | Value | Meaning | Reference |
+-------------+------------------------+---------------+ +-------------+------------------------+---------------+
| TBD2 (0x0B) | RREQ Option | This document | | TBD2 (0x0B) | RREQ Option | This document |
+-------------+------------------------+---------------+ +-------------+------------------------+---------------+
| TBD3 (0x0C) | RREP Option | This document | | TBD3 (0x0C) | RREP Option | This document |
+-------------+------------------------+---------------+ +-------------+------------------------+---------------+
| TBD4 (0x0D) | ART Option | This document | | TBD4 (0x0D) | ART Option | This document |
+-------------+------------------------+---------------+ +-------------+------------------------+---------------+
Figure 7: AODV-RPL Options Figure 7: AODV-RPL Options
10. Security Considerations 10. Security Considerations
In general, the security considerations for the operation of AODV-RPL The security considerations for the operation of AODV-RPL are similar
are similar to those for the operation of RPL (as described in to those for the operation of RPL (as described in Section 19 of the
Section 19 of the RPL specification [RFC6550]). Sections 6.1 and 10 RPL specification [RFC6550]). Sections 6.1 and 10 of [RFC6550]
of [RFC6550] describe RPL's security framework, which provides data describe RPL's optional security framework, which AODV-RPL relies on
confidentiality, authentication, replay protection, and delay to provide data confidentiality, authentication, replay protection,
protection services. Additional analysis for the security threats to and delay protection services. Additional analysis for the security
RPL can be found in [RFC7416]. threats to RPL can be found in [RFC7416].
A router can join a temporary DAG created for a secure AODV-RPL route A router can join a temporary DAG created for a secure AODV-RPL route
discovery only if it can support the Security Configuration in use, discovery only if it can support the security configuration in use
which also specifies the key in use. It does not matter whether the (see Section 6.1 of [RFC6550]), which also specifies the key in use.
key is preinstalled or dynamically acquired. The router must have It does not matter whether the key is preinstalled or dynamically
the key in use before it can join the DAG being created for a secure acquired. The router must have the key in use before it can join the
P2P-RPL route discovery. DAG being created for secure route discovery.
If a rogue router knows the key for the Security Configuration in If a rogue router knows the key for the security configuration in
use, it can join the secure AODV-RPL route discovery and cause use, it can join the secure AODV-RPL route discovery and cause
various types of damage. Such a rogue router could advertise false various types of damage. Such a rogue router could advertise false
information in its DIOs in order to include itself in the discovered information in its DIOs in order to include itself in the discovered
route(s). It could generate bogus RREQ-DIO, and RREP-DIO messages route(s). It could generate bogus RREQ-DIO, and RREP-DIO messages
carrying bad routes or maliciously modify genuine RREP-DIO messages carrying bad routes or maliciously modify genuine RREP-DIO messages
it receives. A rogue router acting as the OrigNode could launch it receives. A rogue router acting as the OrigNode could launch
denial-of-service attacks against the LLN deployment by initiating denial-of-service attacks against the LLN deployment by initiating
fake AODV-RPL route discoveries. In this type of scenario, RPL's fake AODV-RPL route discoveries. When rogue routers might be
preinstalled mode of operation, where the key to use for a P2P-RPL present, RPL's preinstalled mode of operation, where the key to use
route discovery is preinstalled, SHOULD be used. for route discovery is preinstalled, SHOULD be used.
When a RREQ-DIO message uses the source routing option by setting the When a RREQ-DIO message uses the source routing option by setting the
H bit to 0, a rogue router may populate the Address Vector field with H bit to 0, a rogue router may populate the Address Vector field with
a set of addresses that may result in the RREP-DIO traveling in a a set of addresses that may result in the RREP-DIO traveling in a
routing loop. The TargNode MUST NOT generate a RREP if one of its routing loop.
addresses is present in the Address Vector. An Intermediate Router
MUST NOT forward a RREP if one of its addresses is present in the
Address Vector.
11. References If a rogue router is able to forge a gratuitous RREP, significant
damage might result.
11.1. Normative References 11. Acknowledgements
The authors thank Pascal Thubert, Rahul Jadhav, and Lijo Thomas for
their support and valuable inputs. The authors specially thank
Lavanya H.M for implementing AODV-RPl in Contiki and conducting
extensive simulation studies.
The authors would like to acknowledge the review, feedback and
comments from the following people, in alphabetical order: Roman
Danyliw, Lars Eggert, Benjamin Kaduk, Tero Kivinen, Erik Kline,
Murray Kucherawy, Warren Kumari, Francesca Palombini, Alvaro Retana,
Ines Robles, John Scudder, Meral Shirazipour, Peter Van der Stok,
Eric Vyncke, and Robert Wilton.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko, [RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko,
"The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206, "The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206,
March 2011, <https://www.rfc-editor.org/info/rfc6206>. March 2011, <https://www.rfc-editor.org/info/rfc6206>.
skipping to change at page 22, line 9 skipping to change at page 23, line 22
[RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N., [RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N.,
and D. Barthel, "Routing Metrics Used for Path Calculation and D. Barthel, "Routing Metrics Used for Path Calculation
in Low-Power and Lossy Networks", RFC 6551, in Low-Power and Lossy Networks", RFC 6551,
DOI 10.17487/RFC6551, March 2012, DOI 10.17487/RFC6551, March 2012,
<https://www.rfc-editor.org/info/rfc6551>. <https://www.rfc-editor.org/info/rfc6551>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
11.2. Informative References 12.2. Informative References
[co-ioam] Ballamajalu, Rashmi., S.V.R., Anand., and Malati Hegde, [co-ioam] Ballamajalu, Rashmi., S.V.R., Anand., and Malati Hegde,
"Co-iOAM: In-situ Telemetry Metadata Transport for "Co-iOAM: In-situ Telemetry Metadata Transport for
Resource Constrained Networks within IETF Standards Resource Constrained Networks within IETF Standards
Framework", 2018 10th International Conference on Framework", 2018 10th International Conference on
Communication Systems & Networks (COMSNETS) pp.573-576, Communication Systems & Networks (COMSNETS) pp.573-576,
Jan 2018. Jan 2018.
[contiki] Contiki contributors, "The Contiki Open Source OS for the [contiki] Contiki contributors, "The Contiki Open Source OS for the
Internet of Things (Contiki Version 2.7)", Nov 2013, Internet of Things (Contiki Version 2.7)", Nov 2013,
skipping to change at page 23, line 22 skipping to change at page 24, line 34
and M. Richardson, Ed., "A Security Threat Analysis for and M. Richardson, Ed., "A Security Threat Analysis for
the Routing Protocol for Low-Power and Lossy Networks the Routing Protocol for Low-Power and Lossy Networks
(RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015, (RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015,
<https://www.rfc-editor.org/info/rfc7416>. <https://www.rfc-editor.org/info/rfc7416>.
[RFC7548] Ersue, M., Ed., Romascanu, D., Schoenwaelder, J., and A. [RFC7548] Ersue, M., Ed., Romascanu, D., Schoenwaelder, J., and A.
Sehgal, "Management of Networks with Constrained Devices: Sehgal, "Management of Networks with Constrained Devices:
Use Cases", RFC 7548, DOI 10.17487/RFC7548, May 2015, Use Cases", RFC 7548, DOI 10.17487/RFC7548, May 2015,
<https://www.rfc-editor.org/info/rfc7548>. <https://www.rfc-editor.org/info/rfc7548>.
[RFC9030] Thubert, P., Ed., "An Architecture for IPv6 over the Time-
Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)",
RFC 9030, DOI 10.17487/RFC9030, May 2021,
<https://www.rfc-editor.org/info/rfc9030>.
Appendix A. Example: Using ETX/RSSI Values to determine value of S bit Appendix A. Example: Using ETX/RSSI Values to determine value of S bit
The combination of Received Signal Strength Indication(downstream) The combination of Received Signal Strength Indication(downstream)
(RSSI) and Expected Number of Transmissions(upstream)" (ETX) has been (RSSI) and Expected Number of Transmissions(upstream) (ETX) has been
tested to determine whether a link is symmetric or asymmetric at tested to determine whether a link is symmetric or asymmetric at
intermediate nodes. We present two methods to obtain an ETX value intermediate nodes. We present two methods to obtain an ETX value
from RSSI measurement. from RSSI measurement.
Method 1: In the first method, we constructed a table measuring RSSI Method 1: In the first method, we constructed a table measuring RSSI
vs ETX using the Cooja simulation [cooja] setup in the Contiki OS vs ETX using the Cooja simulation [cooja] setup in the Contiki OS
environment[contiki]. We used Contiki-2.7 running 6LoWPAN/RPL environment[contiki]. We used Contiki-2.7 running 6LoWPAN/RPL
protocol stack for the simulations. For approximating the number protocol stack for the simulations. For approximating the number
of packet drops based on the RSSI values, we implemented simple of packet drops based on the RSSI values, we implemented simple
logic that drops transmitted packets with certain pre-defined logic that drops transmitted packets with certain pre-defined
ratios before handing over the packets to the receiver. The ratios before handing over the packets to the receiver. The
packet drop ratio is implemented as a table lookup of RSSI ranges packet drop ratio is implemented as a table lookup of RSSI ranges
mapping to different packet drop ratios with lower RSSI ranges mapping to different packet drop ratios with lower RSSI ranges
resulting in higher values. While this table has been defined for resulting in higher values. While this table has been defined for
the purpose of capturing the overall link behavior, it is highly the purpose of capturing the overall link behavior, it is highly
recommended to conduct physical radio measurement experiments, in recommended to conduct physical radio measurement experiments, in
general. By keeping the receiving node at different distances, we general. By keeping the receiving node at different distances, we
let the packets experience different packet drops as per the let the packets experience different packet drops as per the
described method. The ETX value computation is done by another described method. The ETX value computation is done by another
module which is part of RPL Objective Function implementation. module which is part of RPL Objective Function implementation.
Since ETX value is reflective of the extent of pakcet drops, it Since ETX value is reflective of the extent of packet drops, it
allowed us to prepare a useful ETX vs RSSI table. ETX versus RSSI allowed us to prepare a useful ETX vs RSSI table. ETX versus RSSI
values obtained in this way may be used as explained below: values obtained in this way may be used as explained below:
Source---------->NodeA---------->NodeB------->Destination Source---------->NodeA---------->NodeB------->Destination
Figure 8: Communication link from Source to Destination Figure 8: Communication link from Source to Destination
+-------------------------+----------------------------------------+ +-------------------------+----------------------------------------+
| RSSI at NodeA for NodeB | Expected ETX at NodeA for NodeB->NodeA | | RSSI at NodeA for NodeB | Expected ETX at NodeA for NodeB->NodeA |
+-------------------------+----------------------------------------+ +-------------------------+----------------------------------------+
skipping to change at page 24, line 46 skipping to change at page 26, line 15
received RSSI from NodeB. Whenever nodeA determines that the link received RSSI from NodeB. Whenever nodeA determines that the link
towards the nodeB is bi-directional asymmetric then the S bit is set towards the nodeB is bi-directional asymmetric then the S bit is set
to 0. Afterwards, the link from NodeA to Destination remains to 0. Afterwards, the link from NodeA to Destination remains
designated as asymmetric and the S bit remains set to 0. designated as asymmetric and the S bit remains set to 0.
Appendix B. Changelog Appendix B. Changelog
Note to the RFC Editor: please remove this section before Note to the RFC Editor: please remove this section before
publication. publication.
B.1. Changes from version 09 to version 10 B.1. Changes from version 10 to version 11
o Numerous editorial improvements.
o Replace Floor((7+(Prefix Length))/8) by Ceil(Prefix Length/8) for
simplicity and ease of understanding.
o Use "L field" instead of "L bit" since L is a two-bit field.
o Improved the procedures in section 6.2.1.
o Define the S bit of the data structure a node uses to represent
whether or not the RREQ instance is for a symmetric or an
asymmetric route. This replaces text in the document that was a
holdover from earlier versions in which the RREP had an S bit for
that purpose.
o Quote terminology from AODV that has been identified as possibly
originating in language reflecting various kinds of bias against
certain cultures.
o Clarified the relationship of AODV-RPL to RPL.
o Eliminated the "Point-to-Point" terminology to avoid suggesting
only a single link.
o Modified certain passages to better reflect the possibility that a
node might have multiple IP addresses.
o "Rsv" replaced by "X X" for reserved field.
o Added mandates for reserved fields, and replaces some ambiguous
language phraseology by mandates.
o Replaced "retransmit" terminology by more correct "propagate"
terminology.
o Added text about determining link symmetry near Figure 5.
o Mandated checking the Address Vector to avoid routing loops.
o Improved specification for use of the Shift value in
Section 6.3.3.
o Corrected the wrong use of RREQ-Instance to be RREP-Instance.
o Referred to Subregistry values instead of Registry values in
Section 9.
o Sharpened language in Section 10, eliminated misleading use of
capitalization in the words "Security Configuration".
o Added acknowledgements and contributors.
B.2. Changes from version 09 to version 10
o Changed the title for brevity and to remove acronyms. o Changed the title for brevity and to remove acronyms.
o Added "Note to the RFC Editor" in Section 9. o Added "Note to the RFC Editor" in Section 9.
o Expanded DAO and P2MP in Section 1. o Expanded DAO and P2MP in Section 1.
o Reclassified [RFC6998] and [RFC7416] as Informational. o Reclassified [RFC6998] and [RFC7416] as Informational.
o SHOULD changed to MUST in Section 4.1 and Section 4.2. o SHOULD changed to MUST in Section 4.1 and Section 4.2.
o Several editorial improvements and clarifications. o Several editorial improvements and clarifications.
B.2. Changes from version 08 to version 09 B.3. Changes from version 08 to version 09
o Removed section "Link State Determination" and put some of the o Removed section "Link State Determination" and put some of the
relevant material into Section 5. relevant material into Section 5.
o Cited security section of [RFC6550] as part of the RREP-DIO o Cited security section of [RFC6550] as part of the RREP-DIO
message description in Section 2. message description in Section 2.
o SHOULD has been changed to MUST in Section 4.2. o SHOULD has been changed to MUST in Section 4.2.
o Expanded the terms ETX and RSSI in Section 5. o Expanded the terms ETX and RSSI in Section 5.
o Section 6.4 has been expanded to provide a more precise o Section 6.4 has been expanded to provide a more precise
explanation of the handling of route reply. explanation of the handling of route reply.
o Added [RFC7416] in the Security Considerations (Section 10) for o Added [RFC7416] in the Security Considerations (Section 10) for
RPL security threats. Cited [RFC6550] for authenticated mode of RPL security threats. Cited [RFC6550] for authenticated mode of
operation. operation.
o Appendix A has been mostly re-written to describe methods to o Appendix A has been mostly re-written to describe methods to
determine whether or not the 'S' bit should be set to 1. determine whether or not the S bit should be set to 1.
o For consistency, adjusted several mandates from SHOULD to MUST and o For consistency, adjusted several mandates from SHOULD to MUST and
from SHOULD NOT to MUST NOT. from SHOULD NOT to MUST NOT.
o Numerous editorial improvements and clarifications. o Numerous editorial improvements and clarifications.
B.3. Changes from version 07 to version 08 B.4. Changes from version 07 to version 08
o Instead of describing the need for routes to "fulfill the o Instead of describing the need for routes to "fulfill the
requirements", specify that routes need to "satisfy the Objective requirements", specify that routes need to "satisfy the Objective
Function". Function".
o Removed all normative dependencies on [RFC6997] o Removed all normative dependencies on [RFC6997]
o Rewrote Section 10 to avoid duplication of language in cited o Rewrote Section 10 to avoid duplication of language in cited
specifications. specifications.
skipping to change at page 26, line 24 skipping to change at page 29, line 5
o Specified behavior upon reception of a RREQ-DIO or RREP-DIO o Specified behavior upon reception of a RREQ-DIO or RREP-DIO
message for an already existing DODAGID (e.g, Section 6.4). message for an already existing DODAGID (e.g, Section 6.4).
o Fixed numerous language issues in IANA Considerations Section 9. o Fixed numerous language issues in IANA Considerations Section 9.
o For consistency, adjusted several mandates from SHOULD to MUST and o For consistency, adjusted several mandates from SHOULD to MUST and
from SHOULD NOT to MUST NOT. from SHOULD NOT to MUST NOT.
o Numerous editorial improvements and clarifications. o Numerous editorial improvements and clarifications.
B.4. Changes from version 06 to version 07 B.5. Changes from version 06 to version 07
o Added definitions for all fields of the ART option (see o Added definitions for all fields of the ART option (see
Section 4.3). Modified definition of Prefix Length to prohibit Section 4.3). Modified definition of Prefix Length to prohibit
Prefix Length values greater than 127. Prefix Length values greater than 127.
o Modified the language from [RFC6550] Target Option definition so o Modified the language from [RFC6550] Target Option definition so
that the trailing zero bits of the Prefix Length are no longer that the trailing zero bits of the Prefix Length are no longer
described as "reserved". described as "reserved".
o Reclassified [RFC3561] and [RFC6998] as Informative. o Reclassified [RFC3561] and [RFC6998] as Informative.
o Added citation for [RFC8174] to Terminology section. o Added citation for [RFC8174] to Terminology section.
B.5. Changes from version 05 to version 06 B.6. Changes from version 05 to version 06
o Added Security Considerations based on the security mechanisms o Added Security Considerations based on the security mechanisms
defined in [RFC6550]. defined in [RFC6550].
o Clarified the nature of improvements due to P2P route discovery o Clarified the nature of improvements due to P2P route discovery
versus bidirectional asymmetric route discovery. versus bidirectional asymmetric route discovery.
o Editorial improvements and corrections. o Editorial improvements and corrections.
B.6. Changes from version 04 to version 05 B.7. Changes from version 04 to version 05
o Add description for sequence number operations. o Add description for sequence number operations.
o Extend the residence duration L in section 4.1. o Extend the residence duration L in section 4.1.
o Change AODV-RPL Target option to ART option. o Change AODV-RPL Target option to ART option.
B.7. Changes from version 03 to version 04 B.8. Changes from version 03 to version 04
o Updated RREP option format. Remove the T bit in RREP option. o Updated RREP option format. Remove the T bit in RREP option.
o Using the same RPLInstanceID for RREQ and RREP, no need to update o Using the same RPLInstanceID for RREQ and RREP, no need to update
[RFC6550]. [RFC6550].
o Explanation of Shift field in RREP. o Explanation of Shift field in RREP.
o Multiple target options handling during transmission. o Multiple target options handling during transmission.
B.8. Changes from version 02 to version 03 B.9. Changes from version 02 to version 03
o Include the support for source routing. o Include the support for source routing.
o Import some features from [RFC6997], e.g., choice between hop-by- o Import some features from [RFC6997], e.g., choice between hop-by-
hop and source routing, the L bit which determines the duration of hop and source routing, the L field which determines the duration
residence in the DAG, MaxRank, etc. of residence in the DAG, MaxRank, etc.
o Define new target option for AODV-RPL, including the Destination o Define new target option for AODV-RPL, including the Destination
Sequence Number in it. Move the TargNode address in RREQ option Sequence Number in it. Move the TargNode address in RREQ option
and the OrigNode address in RREP option into ADOV-RPL Target and the OrigNode address in RREP option into ADOV-RPL Target
Option. Option.
o Support route discovery for multiple targets in one RREQ-DIO. o Support route discovery for multiple targets in one RREQ-DIO.
o New RPLInstanceID pairing mechanism. o New RPLInstanceID pairing mechanism.
Appendix C. Contributors Appendix C. Contributors
Abdur Rashid Sangi Abdur Rashid Sangi
Huaiyin Institute of Technology Huaiyin Institute of Technology
No.89 North Beijing Road, Qinghe District No.89 North Beijing Road, Qinghe District
Huaian 223001 Huaian 223001
P.R. China P.R. China
Email: sangi_bahrian@yahoo.com Email: sangi_bahrian@yahoo.com
Malati Hegde
Indian Institute of Science
Bangalore 560012
India
Email: malati@iisc.ac.in
Mingui Zhang
Huawei Technologies
No. 156 Beiqing Rd. Haidian District
Beijing 100095
P.R. China
Email: zhangmingui@huawei.com
Authors' Addresses Authors' Addresses
Satish Anamalamudi Satish Anamalamudi
SRM University-AP SRM University-AP
Amaravati Campus Amaravati Campus
Amaravati, Andhra Pradesh 522 502 Amaravati, Andhra Pradesh 522 502
India India
Email: satishnaidu80@gmail.com Email: satishnaidu80@gmail.com
Mingui Zhang
Huawei Technologies
No. 156 Beiqing Rd. Haidian District
Beijing 100095
China
Email: zhangmingui@huawei.com
Charles E. Perkins Charles E. Perkins
Lupin Lodge Lupin Lodge
Los Gatos 95033 Los Gatos 95033
United States United States
Email: charliep@computer.org Email: charliep@computer.org
S.V.R Anand S.V.R Anand
Indian Institute of Science Indian Institute of Science
Bangalore 560012 Bangalore 560012
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